This invention relates to a method of operating an electrolyte circulation type battery stack of secondary cells operable in a charge mode storing electrical power from a source of electrical power and in a discharge mode discharging the stored electrical power from the secondary battery stack to an electrical load with electrolytes circulating to each secondary cell.
Solar batteries have been developed to convert the sunlight into electrical power. Such solar batteries have a great advantageous potential of supplying electrical power in islets, secluded places, and other areas where no commercial electrical power is available. It is desired to connect a solar battery to a secondary battery so as to store a dump power in daytimes during which the sunlight is sufficient to allow the solar battery to generate electrical power for use in supplying electrical power in night or times such as cloudy or rainy days during which the sunlight is too weak to allow the solar battery to generate electrical power. For this purpose, it is the current practice to connect a lead acid or alkaline secondary battery to a solar battery. However, lead acid or alkaline secondary batteries are not satisfactory in view of size and cost considerations, although they reach completion.
In order to provide a solution for the size and cost problems, it has been proposed to use an electrolyte circulation type secondary battery, such as a zinc-bromine, zinc-chlorine, or redox-flow battery, which operates in charge and discharge modes with electrolytes circulating in the battery. However, such an electrolyte circulation type secondary battery requires an additional source of electrical power to drive electric pumps to circulate the electrolytes. This requirement creates a serious problem in using such a solar battery system in areas where no commercial electrical power is available.